Fabric soaking operations have been described in the art. In such soaking operations, fabrics are left in contact with a soaking liquor for a prolonged period of time typically ranging from a few minutes to overnight or even 24 hours. This laundering process has the advantage that it maximises the contact time between the fabrics and the key active ingredients of the soaking liquor. It also has the advantage that it reduces or eliminates the need for a typical laundering operation involving the need for mechanical agitation, or that it improves the efficiency of the subsequent typical laundering operation.
Such soaking operations are typically desirable to remove tough outdoor dirt from fabrics, such as particulate soil like mud, silt and/or clays. For example, clays usually have a microcrystalline mineral structure (e.g., hydrous aluminium silicate like illite, montmorillonite, kaolinite and the like) with the presence of an organic fraction. The organic fraction can contain a variety of compounds (e.g., humic acid, fulvic acid, plant/animal biomass and the like). Clays can also contain several kinds of metals (e.g., magnesium, calcium, potassium, iron and the like). However, such particulate soil is particularly difficult to remove from fabrics. Indeed, it is believed that the very fine dirt grains like clays or silt, typically below 0.002 mm in size, can insert among fabric fibers and steadily stick to the surface of the fibers. This problem is particularly acute with socks which are most exposed to silt and clay pick-up. Also such soaking operations are not fully satisfactory regarding the stain removal performance delivered on enzymatic stains or even on bleachable stains. Enzymatic stains are typically composed of carbohydrates and proteinaceus soil, like blood. It has now been observed that enzymatic stains may act as a glue for particulate soil on fabrics, thus removing such enzymatic stains may facilitate the removal of particulate soil from fabrics.
It is thus an object of the present invention to improve the stain removal of particulate soils, mud and/or clay, as well as of enzymatic stains and bleachable stains.
It has been found that this object can be met by soaking fabrics in an aqueous soaking liquor comprising an effective amount of a granular soaking detergent composition comprising an oxygen bleach, an anionic surfactant of the formula R-SO3M, wherein R is a substituted or unsubstituted, saturated or unsaturated, linear or branched hydrocarbon chain having from 6 to 40 carbon atoms and M is H or a cation, and a sorbitan ester, as described herein after. Indeed, it has been found that by combining sorbitan ester and such an anionic surfactant as described herein, on top of an oxygen bleach, in a soaking composition, improved stain removal performance is delivered on stains like tough outdoor dirt like particulate soil, bleachable stains as well as enzymatic stains, when used under soaking conditions (i.e., when left in contact for prolonged period of time typically up to 24 hours), as compared to the stain removal performance delivered with the same composition being free of such a sorbitan ester and/or anionic surfactant as described herein.
An advantage of the present invention is that not only improved particulate soil removal performance is delivered but also that the soil redeposition on fabrics in prolonged soaking condition is prevented. Furthermore, the soaking compositions of the present invention comprising sorbitan ester, such an anionic surfactant and oxygen bleach also provide effective stain removal performance on other types of stains like greasy stains, e.g., dirty motor oil, spaghetti sauce.
An advantage of the present invention is that the stain removal performance, when soaking a fabric in presence of a soaking composition comprising an oxygen bleach, such an anionic surfactant and a sorbitan ester, is improved even in the presence of relatively high levels of hardness ions. Indeed, the presence of hardness ions (calcium or magnesium ions), which occur naturally in the soaking liquor, in particular, can reduce surfactant performance and eventually precipitate the surfactant from the soaking liquor as a calcium or magnesium salt. This phenomen occurs less when using a sorbitan ester together with an anionic sulphonate surfactant as defined herein. Accordingly, the soaking detergent manufacturer may make use of builders which are not the more performing at sequestering free hardness ions, and thus may use less expensive builders in such a soaking composition.